Apparatus for use in suspending casing from a wellhead



Oct. 8, 1968 B. H. NELSON E AL 3,404,736

APPARATUS FOR USE IN SUSPENDING CASING FROM A WELLHEAD Filed Feb. 17, 1967 x 4 Sheets-Sheet l Eoy /1 e/J0/7 Zea/70rd L W////amJ INVENTORJ APPARATUS FOR USE IN SUSPENDING CASING FROM A WELLHEAD 4 Sheets-Sheet 2 Filed Feb. 17, 1967 m mm wflw 0 W v I n M 1 .5 6 H Oct. 8; 1968 NELSON ETAL 3,404,736

APPARATUS FOR USE IN SUSPENDING CASING FROM A WELLHEAD Filed Feb. 17, 1967 4 Sheets$heet 3 m nm 0/ J/ W Hf M y m 61 I NVENTORS ATTOA /VV J B. H. NELSON ET AL 3,404,736

Oct. 8, 1968 APPARATUS FOR USE IN SUSPENDING CASING FROM A WELLHEAD v 4 Sheets-Sheet Filed Feb. 17, 1967 United States Patent 3,404,736 APPARATUS FOR USE IN SUSPENDING CASING FROM A WELLHEAD Bobby H. Nelson and Leonard E. Williams, Houston, Tex., assignors to Cameron Iron Works, Inc., Houston, Tex. Continuation-impart of application Ser. No. 365,661, May 7, 1964. This application Feb. 17, 1967, Ser.

. 24 Claims. (Cl. 16685) ABSTRACT OF THE DISCLOSURE Wellhead apparatus comprising a casing head and a hanger laudable on a seat in the bore of the head. Passages through the hanger connect annular spaces above and below the seat, and a seal assembly lowered into the upper space closes the passages. The assembly includes a first tubular body threadedly connectible to the hanger, a second tubular body threaded to the first body, an inner ring for sealing against the hanger, and an outer ring intermediate shoulders on the bodies for sealing against the bore upon shearing of a pin and relative vertical movement between the bodies. A running tool has pins releasably disposable within and selectively engageable with opposite ends of a circumferential groove in the second body to transmit torque in opposite directions. 1

This application is a continuation-in-part of Ser. No. 365,661, filed May 7, 1964, and entitled Wellhead Ap* paratus, now abandoned. This invention relates to well apparatus generally, and, more particularly, to apparatus for use in completing oil and gas wells. In one of its novel aspects, this invention relates to improved apparatus for use in suspending casing from a wellhead located at an underwater level.

Prior apparatus of this type is shown and described in Pat. No. 3,179,448. In such prior apparatus, pressure control equipment is connected to the upper end of the wellhead and the casing is lowered into the well through such equipment for suspension from the wellhead. For this purpose, a mandrel connected to the upper end of the casing has means thereon for releasable connection to a running tool suspended from the lower end of a pipe string and a seat thereabout for landing on a seat in the bore of the wellhead as it is lowered by the tool. After the mandrel has been landed, the casing is anchored in place by means of cement which is conducted downwardly through the pipe string and upwardly into the annulus between the casing and well bore. There are flow passages through the mandrel which connect the annulus with the bore of the wellhead above the seat so that returns may be taken up through them.

The prior apparatus also includes an assembly which is lowered onto the mandrel for closing the flow passages by sealing off the annular space between the mandrel and bore of the wellhead. This assembly comprises a tubular body having threads about it for making up with the mandrel so as to anchor it thereto, a seal ring carried about the inner circumference of the body for sealing between it and the mandrel as the threads are initially made up, and another seal ring carried about the outer circumference of the body for sealing between said body and the bore of the wellhead as the threads continue to be made up. The seal assembly body is releasably attachable to another running tool by means of which it is both lowered through the pressure control equipment and onto the mandrel and then rotated so as to threadedly engage it with the mandrel in the manner described.

In the particular embodiment of this apparatus illustrated in the aforementioned patent, the mandrel has right-hand threads about its upper end for releasably attaching it to threads of the running tool. Thus, when the casing has been cemented within the well, left-hand torque is applied to the drill string to release the running tool from the mandrel and thereby permit it to be removed from the well. The tubular body of the seal assembly also has right-hand threads thereon for making up with the same threads on the mandrel when the mandrel running tool has been so removed and the seal assembly body has been lowered onto the mandrel.

The outer seal ring of the seal assembly is longitudinally slidable along the outer circumference of the assembly body and is carried in a relaxed or retracted state as the assembly is lowered through the pressure control equipment. As the assembly body is initially made up with the mandrel, this seal ring lands on a shoulder above the seat on the mandrel. However, since it is slidable over the outer circumference of the mandrel, it does not interfere with the continued makeup of the body with the mandrel, and a flange projecting outwardly from the upper end of the body moves downwardly toward the seal ring. Upon still further makeup of the body, the flange bears against the ring to expand it radially into sealing engagement with such body and the bore of the wellhead, thereby cooperating with the seal already provided by the inner seal ring to complete the closure of the mandrel flow passages.

As also shown in the particular embodiment of the apparatus shown in the aforementioned patent, this running tool for the seal assembly includes one or more torque transmitting pins vertically movable into and out of slots on the body of the seal assembly, and springpressed balls or other releasable retaining means engageable beneath a shoulder on the body for suspending the body from the tool with the pins held in the slots. Thus, upon anchoring of the seal assembly body to the mandrel and expansion of the seal ring into sealing engagement, an upward pull may be taken on the running tool to release it from the seal assembly and permit it to be removed upwardly from the drilling control assembly. On the other hand, in the event the seal assembly is found not to hold the desired pressure, left-hand torque may be applied to the running tool to threadedly disengage the body of the seal assembly from the mandrel and permit both the running tool and seal assembly to be removed upwardly from the pressure control equipment.

Although this earlier embodiment constitutes a considerable advance over the prior art, there is nevertheless some danger in unthreading one of the joints of pipe making up the string for the mandrel running tool rather than the connection of such tool to the mandrel-as left hand torque is applied to the string in removing the running tool from the mandrel. Even though an attempt was made to overcome this problem by the use of relatively easy threads on the mandrel and its running tool, there is still some risk involved in backing the running tool off from the mandrel.

Also, although the seal assembly of this earlier embodiment is lowered into the pressure control equipment with the outer seal ring in a relaxed state, there is nevertheless a possibility of prematurely expanding it into a position in which it would interfere with the free movement of the seal assembly. Thus, in the event the lower side of the seal ring engages some irregularity in the bore above the mandrel shoulder on which it is to land, continued lowering of the running tool will cause the seal ring to be expanded out into sealing engagement between the body and bore of the wellhead even before anchoring of the body to the mandrel,

Still a further problem arises in the suspension of the seal assembly body from the above-described running tool when it is lowered into the wellhead bore, as well as when it is raised from such bore, in the event the seal assembly does not hold pressure. Thus, the spring pressure on the retaining balls must be strong enough to maintain the suspension, without being so strong as to make it difficult to detach the running tool from the seal assembly body. In deference to the latter, such retaining means may not securely suspend the seal assembly body.

Yet another problem which may be encountered in the use of apparatus of this type is the large hanger load which the seat in the bore of the head must carry, particularly in larger diameter bores. Of course, one solution to this problem is to provide larger seats on the hanger and head. However, this requires a still larger bore across which the apparatus must seal.

An object of this invention is to provide apparatus for suspending casing including a combination casing hanger and seal assembly of the type above-described wherein the seal assembly is of such construction that the outer seal ring is not prematurely expanded by engagement with irregularities in the bores of the pressure control equipment or wellhead above the mandrel shoulder.

Another object is to provide apparatus of the character described in the foregoing object in which the outer seal ring may be retracted and the seal assembly pulled in the event such ring does not hold the desired pressure.

A further object is to provide apparatus comprising a pair of well members, such as the above-described mandrel and seal assembly, wherein one such member is to be run into a well by a running tool suspended from a pipe string and the other member is to be then threadedly connected to the first member when run into the well, but in which said first member is so constructed that it may be lowered by and released from its running tool without danger of unthreading the pipe making up the string Still another object is to provide apparatus for running and then connecting one member to another within a well, as is required in the case of the above-described seal assembly, without danger of dropping such one member, and yet without making it difiicult to remove the running tool therefrom when its threaded engagement is accomplished.

Yet another object is to provide apparatus of this type in which only a portion of the load must be carried by the seat in the head; and, more particularly, in which the remaining portion is carried by another seat in the head in such a way that the size of its bore need not be increased.

These and other objects are accomplished, in accordance with the illustrated embodiments of the present invention by wellhead apparatus in which the assembly for sealing the flow passages through the mandrel comprises first and second threadedly attached tubular bodies having a seal ring disposed between outer shoulders thereupon so as to be protected from the aforementioned irregularities. More particularly, the seal assembly is lowerable onto the mandrel from which the casing is suspended, and the first body thereof has means thereon for releasably anchoring it to the mandrel when the assembly is so lowered and means for sealing between it and the mandrel when such body is anchored thereto. The second body has means thereon releasably attachable to a running tool for lowering the seal assembly into the bore of the casing head and onto the casing hanger, whereby the first body may be anchored and sealed with respect thereto, as above-noted.

As the seal assembly is run into the well bore, the first and second bodies thereof are connected with the threads therebetween less than fully made up with one another to space the shoulders at sufiicient distance apart to permit the seal ring to be relaxed. However, the connection of the second body to the first body is releasable, upon anchoring of the first body to the casing hanger, to permit the threads therebetween to be further made up and the second body to be moved downwardly relative to the first body. The upwardly facing shoulder on the first body is limited against downward movement by virtue of its being anchored to the mandrel, so that the seal ring will be expanded into sealing engagement with the casing head bore by the downward movement of the downwardly facing shoulder on the spaced body. v

In one embodiment of the invention, which is particularly well suited to large diameter casing head bores, there is a groove about a cylindrical portion of the bore above the seat and a rigid, radially expansible ring on the seal assembly is adapted to be moved into load transmitting engagement between such assembly and the lower end of the groove. More particularly, the rigid ring is also disposed between the shoulders on the first and second bodies, and is retracted along with the relaxed seal ring as the seal assembly is lowered within the bore. However, upon landing of the assembly and downward movement of the upper shoulder, such rigid ring is radially expanded, along with the seal ring, until it is tightly engaged between the second body on which the upper shoulder is formed and the lower end of said groove.

Inasmuch as the seal ring is supported by the upwardly facing shoulder of the first body, its lower side is shielded from engagement with irregularities in the bores of the pressure control equipment and wellhead. That is, any such irregularities will instead be engaged by the first body of the seal assembly beneath the shoulder thereon supporting the seal ring, so that the running tool can be manipulated in any desired manner to force the first body past the irregularity and into the desired position for anchoring with the mandrel without prematurely expanding the seal ring. The same is true, of course, of the radially expansible rigid ring.

In the preferred form of the apparatus of the present invention, the first seal assembly body is threadedly attachable to the mandrel, and there is a means for limiting such threaded engagement so as to in turn limit downward movement of the first body relative to the mandrel. It is also preferred that, in the running in position, the two bodies of the seal assembly be releasably connected against additional threaded engagement by means of a shear pin between them. Thus, as the first body is being made up with the mandrel, the shear pin will transmit torque from the running tool and the second body to the first body. However, upon anchoring of the first body to the mandrel, the continued transmission of torque in the same direction will shear the pin and thus permit the second body to be further made up with the first body, thereby causing the seal ring to be expanded into sealing engagement between the first body and the bore of the wellhead in the maner above-described, and in the case of the last described embodiment, the rigid ring to be expanded out into the groove in the bore of the head.

In the event the seal assembly is found to hold the desired pressure, the running tool therefor may be detached from it and pulled from the pressure control equipment. On the other hand, the seal assembly may be retrieved from the bore of the wellhead in the event it does not hold pressure and, for this purpose, the running tool for the seal assembly is capable of imparting torque in opposite directions. However, as distinguished from the running tool for the seal assembly shown and described in the earlier application, the running tool of the present invention is releasably attached to the second body of the seal assembly in such a manner as to more securely suspend same without, on the other hand, interfering in any way with the desired function of the tool in raising and lowering the seal assembly as well as in imparting reverse torque thereto.

Thus, the second body of the seal assembly has at least one annular groove about it with abutments at each end and an axial groove connecting the upper end of the body with the annular groove adjacent one of these abutments. The running tool, on the other hand, has a cylindrical portion adapted to fit concentrically of the second body of the seal assembly, and preferably within it, and a pin on the cylindrical portion movable downwardly through the axial groove and rotatably within the annular groove of the second body of the seal assembly. During such rotation, this pin is selectively engageable with the oppositely facing abutments in order to impart rotation to the second body of the seal assembly in either direction. There is also at least one spring-pressed ball on the cylindrical portion of the running tool which is spaced angular'ly from the pin thereon for engaging one of the abutments when thepin is disposed within the annular groove to one side of the axial groove. In this manner, as the seal assembly is being raised and lowered by means of the running tool, the pin can be disposed beneath the ledge or shoulder forming the upper side of the annular groove in the second body and held in such position by means of the spring-pressed ball.

In the preferred embodiment of the invention, the mandrel has two threads about it, one such thread being provided for releasable attachment to the tool for running the mandrel into landed position within the bore of the wellhead and the other thread being provided for making up with the first body of the seal assembly. More particularly, the first-mentioned threads are of the left-hand variety and the second threads of the right-hand variety and so located relative to the left-hand threads as to permit the first body of the seal assembly to be moved over and releasably connected thereto upon removal of the running tool releasably connected to the left-hand threads.

By means of these left-hand threads on the mandrel, it may be run into and landed within the bore of the wellhead, and the running tool then backed off by means of right-hand torque imparted thereto by means of the pipe string. Since the pipe string is made up of joints threadedly connected by right-hand threads, there is no tendency during this release of the running tool from the mandrel to unthread the pipe joints. When the running tool for the mandrel is removed therefrom, the seal assembly may be lowered through the conductor and into the bore of the wellhead for threadedly making up and thereby anchoring tothe mandrel by means of right-hand torque imparted tothe running tool for such seal assembly.

In the drawings, wherein like reference characters are used'throughout to designate like parts:

FIG. 1 is an elevational view, partly in section, of the head of an offshore well located at an underwater level and having pressure control equipment connected to its upper end, the sectional part of such figure showing a mandrel having its upper end connected to a running tool, its lower end connected to the upper end of a casing, and landed on a seat within the bore of the wellhead for suspending a casing string within the well, and constructed in accordance with one embodiment of apparatus constructed in accordance with this invention;

FIG. 2 is an enlarged half-sectional view of the upper end of the mandrel and the running tool shown in FIG. 1;

FIG. 3 is a half-sectional view similar to FIG. 2, but with the running tool released and removed from the mandrel and the seal assembly of such embodiment lowered onto and threadedly engaged with the mandrel by means of another running tool;

FIG. 4 is a view similar to FIG. 3, but wherein the running tooLhas been rotated so as to in turn rotate the second body of the seal assembly for lowering it with respect to the first body and thereby expanding the seal ring of the assembly into sealing engagement between the first body and bore of the wellhead;

FIG. 5 is a cross-sectional view of the running tool and the second body of the seal assembly to which it is releasably attached, as seen along broken line 5-5 of FIG. 3;

FIG. 6 is a cross-sectional view similar to FIG. 5, but as seen along broken line 66 of FIG. 3;

FIG. 7 is a vertical sectional view of the wellhead shown in FIG. 1, on a smaller scale and with the casing hanger shown in FIG. 1 as well as a second casing hanger landed within the bore of the Wellhead, and with the running tool for lowering the seal assembly of the second casing hanger releasably attached thereto;

FIG. 8 is a half-sectional view of another embodiment of apparatus constructed in accordance with this invention, and showing, similarly to FIG. 3, the seal assembly thereof lowered onto and threadedly engaged with the mandrel by means of a running tool shown in phantom; and

FIG. 9 is another half-sectional view of such embodiment, but in which, as in FIG. 4, the running tool has been actuated to expand the seal ring into sealing engagement with the bore and a rigid ring into load transmitting relation between the assembly and a groove in such bore.

With reference now to the details of the above-described drawings, the upper end of the well shown in FIG. 1 includes a conductor casing 10 which has been lowered into a bore hole 11 at the underwater level 12 of an offshore location. A base structure 13 secured about the upper end of conductor casing 10 rests on the level 12, and the conductor casing is anchored within the bore hole 11 by a column 14 of cement about at least a substantial portion of its length.

A casing head 15 of the embodiment of FIGS. 1 to 6 is connected to the upper end of conductor casing 10 by means of a flange 16 having J-slots (not shown) for releasably attaching such flange to pins 17 projecting outwardly from the upper end of the conductor casing. The casing head is spaced from and connected to the flange 16 by guide wings 18 or the like which project downwardly from the flange to fit closely within the conductor casing and thereby center the casing head 15 with respect thereto.

A string of casing 19 is connected to the lower end of the bore 20 through the casing head for extension downwardly through conductor casing 10, and has its lower end anchored within the well by cement (not shown) as well known in the art. Pressure control equipment 21 releasably connected to the upper end of the casing head includes, from its lower end up, a remotely actuable connector 22, one or more blowout preventers 23, and a riser pipe 24 which extends upwardly to the water level (not shown).

Generally, these parts of the pressure control equipment form a continuous bore of substantially the same diameter as the upper end of the bore 20 in the casing head 15, whereby various tools which can be lowered into the casing head bore may be passed through the pressure control equipment. The details of the connector 22, blowout, preventer 23, and the riser pipe 24 as well as the parts for connecting them to one another are unimportant to the novel aspects of the present invention, and therefore are not described in detail. It is merely suflicient to note that the pressure control equipment including the connector 22 is lowerable into and remotely attachable to the upper end of the casing head 15 after such casing head has been positioned as shown in FIG. 1. In this manner, one or more casing strings may then be lowered into and landed within the casing head for suspension within the well, as will be described to follow, while maintaining pressure control over the well.

As shown in FIG. 1, a casing hanger 25 having a casing 25a suspended from its lower end has been lowered through the pressure control equipment 21 and a seat 27 thereon landed on a seat 26 in the bore 20 of the casing head. With the casing hanger 25 so landed, the casing 25a is suspended within the casing .19 in spaced relation thereto to provide an annulus thereabout which extends upwardly to the seat in the bore 20. This annulus is connected to the bore of the casing head 15 above the seat by means of flow passages 28 formed vertically within the casing hanger 25.

The casing hanger 25 of this first-described embodiment comprises a mandrel having an upper portion 29 which is relieved to provide an upwardly facing shoulder 30 above the conical seat 27. As best shown in FIG. 2, a running tool 31 is releasably connected to the upper portion 29 of the mandrel and is suspended from the lower end of a casing string 32, whereby the mandrel with the casing 25a suspended from it may be lowered into the well and the mandrel landed within the bore of the casing head, as previously described.

Again as best shown in FIG. 2, the running tool 31 includes a tubular body 33 having internal threads 34 about its upper end for connection with threads 34a about the lower end of the lowermost joint of easing string 32. There are also internal threads 35 about the lower end of the running tool body 33 for releasable connection with threads 35a about the upper portion 29 of mandrel 25. When these latter threads are made up, an O-ring 33a on the inner circumference of the body 33 is sealably engaged with the upper portion 29 of the mandrel above the threads 35. The outer circumference of the body 33 fits relatively closely within casing head bore 20 as well as the bore of the pressure control equipment 21, but is slotted, as at 3312, to facilitate its being lowered through the bores and to permit upward circulation of returns during cementing.

The casing string 32 extends upwardly to the water level so that cement may be pumped downwardly through it and the casing 25a suspended from the mandrel 25, and then upwardly within the annulus about the casing 25a. During the cementing operation, returns are taken upwardly through the annulus between the casings 19 and 25a from which they pass through the mandrel flow passages 28 into the annulus between the mandrel and running string and bores of the casing head and pressure control equipment for flow upwardly to the water level.

The threads of the couplings of easing string 32, including threads 34a, are right-hand threads. However, threads 35 and 35a are left-hand threads so that they may be disengaged by right-hand turning of the casing string 32. In this manner, upon completion of the cementing operation, the running tool is detached and withdrawn from the casing head and pressure control equipment, and a seal assembly 36 is lowered through the conductor and onto the mandrel 25 in the bore 20 for closing the flow passages 28. As shown in FIG. 3, the seal assembly is lowered by means of a running tool 37 suspended from the lower end of a .drill string 37a.

As shown in FIG. 3, the seal assembly is comprised of a pair of tubular bodies 38 and 39 which are made up with one another by means of threads 40 disposed about the upper end of the body 38 and threads 40a disposed about an intermediate portion of the body 39. The first body 38 has threads 41a about its lower end for making up with threads 41 about the mandrel 25 intermediate the running tool threads 35a of the mandrel and the seat 27 thereabout. More particularly, the threads 41 on the mandrel are arranged radially outwardly of the threads 35a so that the threads 41a on the seal assembly body 38 are free to move downwardly over the threads 35a into position for engagement with the threads '41 on the mandrel. As can be seen from FIG. 3, the seal assembly is guided into position for making up with the mandrel by means of its relatively close fit within the bore 20 of the casing head 15.

The upper end of the second body 39 of the seal assembly is releasably attached to the running tool 37 by means of pins 42 which project outwardly from the body 43 of the running tool for fitting within annular grooves 44 about the inner circumference of the upper end of body 39. As will be described to follow, and as previously-mentioned, this releasable attachment of the running tool to the body 39 of the seal assembly not only permits the entire assembly to be lowered onto the casing hanger, but also permits it to be rotated for anchoring thereto by the engagement of threads 41. Thus, the seal assembly bodies 38 and 39 are releasably connected against rotation relative to one another by means of one or more shear pins 45, so that right-hand torque transmitted to the running tool body 43 by the drill string 37a will be transmitted to the body 39 and thus to the body 38 for making up the threads 41a on the body 38 with the threads 41 on the mandrel 25.

There is a tapered shoulder 46 on the inner circumference of the seal assembly body 38 which seats upon a similarly shaped shoulder 47 on the upper end of the upper portion 29 of mandrel 25 so as to limit the threaded engagement of the body 38 with the mandrel. During this makeup of the seal assembly with the mandrel, an O-ring 48 moves into slidable sealing engagement with the upper portion of the mandrel above the threads 35a. There is an additional seal ring 48a on the tapered shoulder 46 of the body 38 for engaging the shoulder 47 of the mandrel to provide a further seal between these two members when the body 38 is fully made up with the mandrel so as to anchor the seal assembly thereto.

A seal ring 50 surrounds the body 38 and is carried on an upwardly facing shoulder 51 about its outer side. The upper end of this seal ring is disposed opposite a downwardly facing shoulder 52 on the lower end of body 39, In the relative positions of the bodies 38 and 39 when they are connected by shear pin 45, as shown in FIG. 3, the seal ring 50 is relaxed so that its outer circumference is spaced radially inwardly from the bore 20 of the casing head 15. Thus, the seal assembly is free to move through the pressure control equipment and bore of the casing head into the position of FIG. 3.

However, when the body 38 of the seal assembly has been made up with the mandrel 25, and further makeup is limited by engagement of the shoulders on the body and mandrel, continued right-hand torque imparted to the body 39 will cause the pin to be sheared. As a result, the body 39 will be further threadedly engaged with the body 38, thereby causing the shoulder 52 on the lower end of body 39 to move downwardly against seal ring 50. Thus, the seal ring will be expanded radially to sealably engage between the body 38 and the bore 20 of the casing head, as shown in FIG. 4. At this time, the flow passages 28 in the mandrel will be closed off, assuming that the seal between the body 38 and the mandrel 25 as well as the seal between the body 38 and the bore of the casing head will hold the desired pressure.

This ability of the seal assembly to hold pressure is preferably tested by a method which includes the use of the running tool 37. Thus, somewhat is described in Pat. No. 3,177,703, the body 43 of the testing tool carries a cuptype packing 53 thereabout for sealing between such body and the inner circumference of the mandrel 25, as shown in FIG. 3. Test pressure may then be admitted to the annular space between the drill string 37a for the running tool and the bore of the casing head as well as the bore of the pressure control equipment thereabove up to the closed rams of the preventer, so as to determine the pressure holding capacity of the seal assembly.

If the assembly holds the desired test pressure, the running tool 37 is released therefrom and withdrawn from the pressure control equipment above the casing head. On the other hand, if the seal assembly does not test properly, the running tool for it is manipulated to release the assembly from the mandrel and raise it from within the control equipment. For this purpose, and as above-described, the running tool is capable of imparting either right or lefthand torque to the body 39 of the seal assembly. Since right-hand torque is used in making up the connection between the seal assembly and the mandrel and then actuating the seal ring 50, it is obvious that the seal ring would be relaxed and that the body 38 of the seal assemthe seal-assembly and both the mandrel 25 and the bore of the casing head by way of the seal ring 50 which opposes movement of threads 41a.

As shown in FIGS. 3 and 4, a split spring 54 is disposed about the body 38 of the seal assembly partially within a groove 55. Normally, this spring extends radially outwardly of the outer circumference of the body 38, as shown in FIG. 3, so as to be disposed partially within an oppositely facing groove 56a about the inner circumference of body 39, whereby such spring bridges the separation between the bodies. v

For the purpose of completely detaching body 38 from body 39, should this become necessary, one or more crews 56 may be removed and a tool inserted to contract the spring54 wholly into the groove 55 to permit body 39 to be unscrewed upwardly therepast. During setting of the seal assembly in the well, as bodies 38 and 39 are being threaded together to energize the seal ring-50, spring 54 is carried into groove 55, as shown in FIG. 4, by a tapered surface on. the upper side of the groove in the body 39. V

When the body 39 is moved upwardly with respect to body 38, the spring 54 moves-outwardly into a position to be engaged by shoulder 56a on the body 39 adjacent the lower edge of screw 56, as shown in FIG. 3. This, of course, prevents further unthreading of the body 39 with respect to body 38, so thatcontinued left-hand rotation of the body 39 will be transmitted to the body 38 so as to detach threads 41 and 41a and thus release the seal assembly 36 from the mandrel 25. Threads 41 and 41a are relatively easy running compared with the threads connecting the joints of the drill string 37a. Thus, the normal tendency will be to detach these threads rather than disconnect a portion of the drill string. When the seal assembly is detached from the mandrel 25, it can be raised from within the bore of the wellhead and thepressure control equipment 21 by means of the running tool 37.

As shown in FIGS. 5 and 6, there are four circumferentially spaced-apart annular grooves 44 in the upper end ofthe seal assembly body 39. These annular grooves are spaced apart by means of arcuate inserts 58 held within the grooves by screws 59 or the like (see FIG. 5) and providing abutments on their opposite sides. One end of each annular groove 44 connects with an axial groove 60 which, as best shown in FIG. 4, extends to the upper end of body 39. The pins 42 carried by the body 43 of the running tool are free to pass vertically into and out of the axial slots 60.

v The running tool 37 also includes a series of balls 61 which are carried by the body 43 and urged by springs 62 into a retained position within sockets 62a in which they project slightly from the outer circumference of the body 43, as shown in FIGS. 4, 5 and 6. More particularly, these balls engage with an abutment at one end of the groove 44 when the pins 42 are engaged against an abutment at the opposite end of such groove, so as to retain the pins 42 in the positions shown in FIGS. 5 and 6, wherein they are disposed beneath the upper side of the groove 44, and thus in direct supporting position beneath a ledge on the upper end of the body 39.

In the initial attachment of the running tool to the seal assembly, the body 43 is oriented into a position in which the pins 42 are free to move axially into the slots 60, the spring-pressed balls 61 being urged inwardly. The seal assembly is then turned so as to move pins 42 into engagement with an abutment on one side of the adjacent insert 58. The balls 61 will at the same time be moved over the inserts 58 into the position shown in FIGS. 5 and 6. With the seal asseembly thus attached to the running tool 37, the drill string 37a is lowered through the pressure control equipment to lower the seal assembly onto the mandrel.

After the seal assembly is so lowered, right-hand torque is imparted to the running too] causing the balls 61 to retract and the pins 42 to engage the other ends of the grooves 44 and thereby impart right-hand torque to the seal assembly. After the seal assembly has been attached to the mandrel 25, seal ring 50 energized and the seals tested as described above, and assuming that the seal assembly has been found to hold a! desired test pressure, the running tool 37 may be withdrawn.

If the test shows that the seal assembly does not hold a desired pressure, the running tool is rotated in a lefthand direction so as to move the pins 42 into abutment with the opposite ends of the grooves 44 in the position of FIGS. 5 and 6. Continued left-hand rotation of the running tool will then impart left-hand torque to the body 39 which, as previously described, results in relaxing of the seal ring 50 and detachment of the body 38 from the mandrel. Thus, the seal assembly is securely supported from the running tool as it is raised from within the bore of the wellhead and the conductor, the balls 61 serving to prevent accidental rotation of the seal assembly relative to the running tool.

As shown in FIG. 7, after actuation of the seal assembly 36 to close off the flow passages through the mandrel 25, another casing 63 may be suspended within the well concentrically within casing 25a by means of a mandrel type casing hanger 63a lowered onto and landed upon an upwardly facing conical seat 64 on the upper inner circumference of body 38. This mandrel 63a may be similar in many respects to the mandrel 25. Thus, it may have flow passages (not shown) for connecting the annular space between the casings 25a and 63 beneath the seat 64 With the bore of the wellhead above such seat, so that in the cementing of the oil string 63 within the well. bore, cement may be conducted downwardly through the casing 63 and up the annular space about it, with returns being taken through the flow passages in the mandrel 63a.

These flow passages are then closed, similarly to the flow passages 28 through mandrel 25, by a seal assembly 65 lowered onto and anchored with respect to the mandrel 63a in much the same manner as the seal assembly 36 above-described. Thus, as shown in FIG. 7, the seal assembly is so lowered by means of a running tool 66, which may be similar in many respects to the running tool 37, so as to permit right and left-hand rotation to be imparted to the seal assembly.

As can be seen from FIG. 7, the seal assembly 65 seals across the annular space between the mandrel 63a and the bore 20 of the casing head. Also, this seal assembly includes a set of slips 67 or other suitable means for anchoring it within the bore of the wellhead, and thereby holding both the mandrel 63a and the mandrel 25 down within the casing head. More particularly, these slips 67 are so arranged and constructed as to be automatically urged into engagement with the bore of the wellhead as the upper body 65a of the seal assembly 65 is moved downwardly with respect to the lower body 65b thereof in the expansion of the seal ring 650 thereof into sealing engagement with the bore of the casing head. Reference, in this respect, is bad to the aforementioned Pat. No. 3,179,- 448, wherein slips similarly constructed and arranged are disclosed.

Upon landing of the casing hanger 63a and successful actuation of the seal assembly 65 so as to close off the flow passages through the mandrel 63a, the running tool 66 is released from the seal assembly and withdrawn from within the conductor above the casing head. At this time, the well may be completed by the running of tubing and the setting of a Christmas tree, all in a manner which does not form part of the present invention.

The embodiment of the apparatus illustrated in FIGS. 8 and 9, is of course, in many respects similar if not identical in structure and operation to the embodiment of the apparatus previously-described in connection with FIGS. 1 to 7. Consequently, many parts of the apparatus of FIGS. 8 and 9 bear the same references characters as corresponding parts of the previously-described apparatus, except for the addition of a prime. The primary difference in the two embodiments resides in a means for relieving a portion of the load of the hanger from the seat 26' in the bore 20' of the casing head. Thus, there is a groove 70 about the cylindrical portion of the bore 20' above the seat 26', and a rigid ring 71 is disposed about the seal assembly 36' for engaging in load-transmitting relation between such assembly and the lower end of the groove 70. More particularly, and as previously-described, the ring 71 is disposed about the outer side of the assembly intermediate the upper and lower shoulders 52' and 51 on the second tubular body 39 and the first tubular body 38', respectively.

This ring 71 is split about its circumference to permit it to be expanded from the normally retracted position shown in FIG. 8 to the radially expanded position shown in FIG. 9. In the first of these positions, of course, such ring engages along its inner side with the upwardly extending tubular portion of the first tubular body 38' so that its outer side is in substantial alignment with the outer surface of the relaxed seal ring 50' and the outer cylindrical sides of the first and second tubular bodies. When such rigid ring is expanded, however, its inner side moves away from the outer side of the upwardly extending portion of the first body and its outer sides move into engagement with the bottom of the groove 70.

In the preferred form of this apparatus, the rigid ring 71 is disposed between the seal ring 50' and the upwardly facing shoulder 51' on the first body 38. As can be seen from the drawings, this latter shoulder tapers downwardly and outwardly and is so located with respect to the length of the first tubular body 38' that when such body is fully made up with hanger 25, its intersection with the outer side of such body will be substantially adjacent the intersection of the lower, downwardly and inwardly tapering end 72 of groove 70 with the upper cylindrical portion of the casing head bore 20'. More particularly, the lower end of the ring 71 has inner and outer surfaces tapered correspondingly to the shoulder 51' and the lower end 72 of the groove 70, so that as the solid ring is expanded to the FIG. 9 position, the inner surface slides along shoulder 51' until the outer surface engages such lower end of the groove.

The ring 71 is adapted to be wedged downwardly and outwardly along the shoulder 51' by means of a solid expander ring 73 disposed immediately beneath the lower end of the seal ring 50 and having a lower surface 74 which tapers downwardly and inwardly for engaging along a correspondingly tapering surface 75 on the inner side of the upper end of the rigid ring 71.

As will be apparent from a comparison of FIGS. 8 and 9, the expander ring 73 is moved downwardly to so wedge the rigid ring 71 in response to a downward move ment of the seal ring 50 resulting from its deformation due to the downward movement of the second tubular body 39 relative to the first tubular body 38'. When the ring 71 is thus tightly engaged between the shoulder 74 and groove end 72, at least a portion of the load of the hanger which would otherwise be borne by the seat 26 is instead transmitted to a portion of the head above the seat.

Thus, upon landing of the first tubular body 38' of the seal assembly in the manner previously-described in connection with the embodiment of Figs. 1 to 7, the running tool 37' is actuated to thread the second body 39' downwardly along the first tubular body 38'. This, of course, lessens the spacing between the shoulders 51' and 52' to thereby expand the seal ring 50 into sealing engagement with the bore and force the rigid ring 71 into the groove 70. Obviously, full makeup of the threads so 12 as to fully expand the seal'ring 50 also lowers the expander ring 73 into tight, load-transmitting engagement with the rigid ring 71.

Conversely, in the event the seal assembly does not function properly, or if it is desired to remove it forany other reason, reversal of the rotation of running tool 37 raises body 39' relative to body 38', thereby permitting the seal ring 50 to return to its relaxed position and the rigid ring 71 to contract to its normal position shown in FIG. 8. This contraction of the solid ring will, of course, force the expander ring upwardly so as to maintain its upper end in engagement with the lower end of the seal ring 50, in the event it is-separate therefrom. Obviously, however, the expander ring 73 may be attached to the seal ring 50' in some manner.

Preferably, the upper end 76 of the groove 70 and the tapered so as to avoid any sharp corners along the length of the bore 20 which might otherwise interfere with contraction of the ring 71. More particularly, groove end 76 is spaced above the upper end of the expanded ring 71, and such end and ring surface 77 are parallel to shoulder 51 and lower inner surface of the ring to permit it to move upwardly and inwardly without interference.

' From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interperted as illustrative and not in a limiting sense.

The invention having been described, what is claimed l. Wellhead apparatus, comprising a casing head having a bore therein and a seat within the bore, a casing hanger lowerable into the bore and having a seat thereon for landing on the seat in the bore and means for suspending a casing from its lower end, means providing flow passages connecting the annular space about the suspended casing with the casing head bore above the seat therein when the casing hanger is landed on said seat, and an assembly lowerable onto the casing hanger for closing said fiow passages, said assembly including a first tubular body having means thereon for releasably anchoring it to the casing hanger when so lowered, means for sealing between the casing hanger and first body when said first body is anchored to the casing hanger, a second tubular body connected to the first body and having means thereon releasably attachable to a running tool for lowering both bodies into the bore of the casing head and causing said first body to be releasably anchored to said casing hanger, an upwardly facing shoulder on the first body and a downwardly facing shoulder on the second body, and a seal ring disposed between said shoulders, the connection of the second body to the first body being releasable, upon anchoring of said first body to said casing hanger, to permit said second body to be moved downwardly relative to the first body for expanding said seal ring into sealing engagement with said casing head bore.

2. Wellhead apparatus of the character defined in claim 1, wherein said second body is movable upwardly relative to the first body a distance sufiicient to permit the seal ring to retract from sealing engagement with said casing head bore, and said assembly also includes means for connecting the first and second bodies when the second body has been moved upwardly said distance so that the first body may be raised with the second body upon release of the first body from the casing hanger.

3. Wellhead apparatus, comprising a casing head having a bore therein and a seat within the bore, a casing hanger lowerable-into the bore and having a seat thereon for landing on the seat in the bore and means thereon for suspending a casing from its lower end, means providing flow passages connecting the annular space about the suspended casing with the casing head bore above the seat therein when the casing hanger is landed on said seat, and an assembly lowerable onto the casing hanger for closing said fiow passages, said assembly including a first tubular body having means thereon for releasably anchoring it to the casing hanger against vertical movement relative thereto, means for sealing between the casing hanger and first body when said first body is anchored to the casing hanger, a second tubular body having means thereon releasably attachable to a running tool for lowering it into the bore, means connecting the second body to the first body against downward movement relative thereto so as to permit said first body to be lowered with the second body and the means on said first body to be actuated to anchor said first bodyto said casing hanger, and upwardly facing shoulder on the first body and a downwardly facing shoulder on the second body, and a seal ring disposed between said shoulders, said connecting means being releasable, upon anchoring of the first body to the casing hanger, to perm-it the second body to be moved downwardly relative to the first body for expanding said seal ring into sealing engagement with said casing head bore.

4. Wellhead apparatus, comprising a casing head having a bore therein and a seat within the bore, a casing hanger lowerable into the bore and having a seat thereon for landing on the seat in the bore and means thereon for suspending a casing from its lower end, means providing flow passages connecting the annular space about the suspended casing with the casing head bore above the seat therein when the casing hanger is landed on said seat, and an assembly lowerable onto the casing hanger for closing said flow passages, said assembly including a first tubular body having rotatably actuated means thereon for releasably anchoring it to the casing hanger against vertical movement relative thereto, means for sealing between the casing hanger and first body when said first body is anchored to the casing hanger, a second tubular body having means thereon releasably attachable to a running tool for lowering said second body within the bore and imparting rotation thereto, means threadedly engaging the second body with the first body for lowering said first body with said second body into the bore, means connecting the second and first bodies against relative rotation to permit the means on the first body to be actuated for anchoring it to said casing hanger, an upwardly facing shoulder on the first body and a downwardly facing shoulder on the second body, and a seal ring disposed between said shoulders, said connecting means being releasably, upon anchoring of the first body to the casing hanger and additional threaded engagement of the second body with the first body to permit said second body to move downwardly relative to the first body for expanding said seal ring into sealing engagement with said casing head bore.

5. Wellhead apparatus, comprising a casing head having a bore therein and a seat Within the bore, a casing hanger lowerable into the bore and having a seat thereon for landing on the seat in the bore and means thereon for suspending a casing from its lower end, means providing flow passages connecting the annular space about the suspended casing with the casing head bore above the seat therein when the casing hanger is landed on said seat, and an assembly lowerable onto the casing hanger for closing said flow passages, said assembly including \a first tubular body lowerable onto the casing hanger and having threads thereon for engaging with threads on the casing hanger when so lowered, means limiting the threaded engagement of the first body and casing hanger to locate the first body against further rotational and downward movement relative to the casing hanger, means for sealing between the casing hanger and the first body when said first body is threadedly engaged with the casing hanger, a second tubular body having mean-s thereon releasably attachable to a running tool for lowering it into the bore and imparting rotation thereto, means threadedly engaging the second body with the first body for lowering said first body with said second body into the bore, means connecting the second and first bodies against relative rotation so as to permit the threads on the first body to be engaged with those on the casing hanger in response to rotation of the second body, an upwardly facing shoulder on the first body and a downwardly fiacing shoulder on the second body, and a seal ring disposed between said shoulders, said connecting means being releasable, upon said limited threaded engagement of the first body to the casing hanger and in response to continued rotation of said second body, to permit the second body to be moved downwardly relative to the first body for expanding said seal ring into sealing engagement with said casing head bore.

6. Apparatus for use in hanging casing from within the bore of a casing head, comprising a tubular mandrel lowerable into said bore and having a downwardly facing seat about its outer side for landing the mandrel therein, means on the mandrel for suspending a casing from its lower end, the upper portion of the mandrel being relieved above the seat about its outer side, and an assembly lowerable into the bore of the casing head for sealing between said mandrel and said bore, said assembly including a first tubular body having threads thereon engageable with threads about said upper portion of the mandrel, means on the first body engageable with means on the mandrel for limiting their threaded engagement, means sealing between the first body and said mandrel when they have been threadedly engaged, the outer side of said first body having an upwardly facing shoulder thereon, a seal ring carried about the first body above said shoulder, a second tubular body having threads thereon engaged with threads about the first body, a downwardly facing shoulder on the second body disposed above said seal ring, and a pin connecting the first and second bodies against relative movement as said first body is threadedly engaged with the mandrel, said pin being shearable, upon engagement of the limiting means on the first body and mandrel and further threaded engagement of the second body with the first body, to permit the second body to move downwardly with respect to the first body so as to deform said seal ring.

7. Apparatus of the character defined in claim 6, including means on the second body for engaging the first body as it is threadedly backed off from said first body a distance sulficient to permit the seal rings to collapse, whereby continued rotation of the second body will be transmitted to the first body to permit first body to be backed off from the mandrel.

8. A seal assembly, comprising a first tubular body having internal threads thereabout, the upper portion of the outer side of the first body being relieved to provide an upwardly facing shoulder thereabout, a seal ring surrounding the upper portion of the first body above the shoulder, external threads about said upper portion above the seal ring, a second tubular body telescopically disposed about the upper portion of the first body and having threads thereon engaged with the external threads about said upper portion, a shoulder on the lower end of the second body above the seal ring, a shear pin connecting the first and second bodies against relative rotation, oppositely facing grooves about the outer side of the first body and inner side of the second body, respectively, and a split spring partially within each groove to bridge the separation between the bodies, the upper end of the groove about the second body having a cam surface for radially compressing the spring into the groove about the first body, upon shearing of said pin and further threaded engagement of the second body with the first body, so as to move the shoulder on said second body toward the shoulder on the first body and thereby deform said seal ring radially outwardly between said shoulders, said second body being movable upwardly relative ot the first body to return the groove thereabout to a position opposite the groove about the first body so as to permit the spring to move back outwardly into a position bridging the separation between the bodies, and the lower end of the groove about the second body being engageable with the spring so as to prevent further upward movement of the second body relatively to said first body.

9. Wellhead apparatus comprising a wellhead having a bore therein and a seat within the bore, and a casing hanger including a hollow mandrel lowerable through the bore of the casing head and having a seat thereabout for landing on the seat within the bore, means on the mandrel for suspending a casing from its lower end, first and second threads of the opposite hand about the mandrel, said first threads being releasably attachable to a running tool by which the mandrel is so lowered, and an annular seal assembly lowerable through the bore into telescopic relation about the mandrel above the seat on the mandrel upon removal of the running tool therefrom, threads on the seal assembly for making up with second threads about the mandrel as the seal assembly is so lowered and telescopically disposed about the mandrel, and means carried by the seal assembly for sealing between the first body and bore of the casing head when the mandrel and seal assembly are so made up.

10. Wellhead apparatus of the character defined in claim 9, wherein the first and second threads on the mandrel are disposed about longitudinally spaced-apart external portions thereof.

11. Wellhead apparatus of the character defined in claim 9, wherein said seal assembly includes a pair of telescopically arranged tubular bodies having oppositely facing shoulders thereon, said sealing means includes a seal ring disposed between said shoulders, and said tubular bodies are threadedly connected to one another by threads of the same hand as the second threads about the mandrel so as to permit them to be moved longitudinally relative to one another for energizing the seal ring upon making up of the mandrel and seal assembly.

12. Well apparatus, comprising a well conduit having a seat therein, a first cylindrical member having lefthand threads about an external portion thereof for releasable attachment to a running tool to permit said first member to be lowered into the well conduit, a seat on the first member for landing on the well conduit seat when the first member is so lowered, a second cylindrical member adapted to be lowered through the well conduit and about the upper portion of the first member upon removal of the running tool therefrom, and right-hand threads about an external portion of the first member and an internal portion of the second member for threadedly connecting the first and second members as the second member is lowered about the upper portion of the first member.

13. Well apparatus, comprising a first cylindrical member adapted to be lowered into a landed position within the well, left-hand threads externally about the first member for releasable attachment to a running tool, righthand threads externally about said first member, and a second cylindrical member adapted to be lowered through the well into a telescopic fit with respect to the first member, upon release and removal of the running tool from the left-hand threads thereof, and threads about the second cylindrical member for making up with the righthand threads of the first cylinder member as said second member is so fitted.

14. Well apparatus, comprising a cylindrical well member adapted to be moved vertically into a landed positiofi within a well, a tool for so moving the well member, said well member having a least one annular groove thereabout with abutments at each end and an axial groove connecting the upper end of the member with the annular groove adjacent one of said abutments, and said tool having a cylindrical portion adapted to fit concentrically of the Well member, a pin on the cylindrical portion of the tool movable downwardly through the axial groove and rotatably within the annular groove of the well member for selectively engaging with said abutrnents in order to impart rotation to the well member, and a spring-pressed ball on said cylindrical portion of the tool spaced angularly from the pin for engaging with one of said abutments when said pin is disposed within the annular groove to one side of the axial groove. I

15. Wellhead apparatus, comprising a casing head hav' ing a bore therethrough, a seat within the bore, a casing hanger landable on the seat for suspending a casing from its lower end so as to provide inner and outer walls defining annular spaces therebetween above and below said seat, means providing flow passages connecting the annular spaces, and an assembly lowerable within the bore of the casing head and into the upper space to close said flow passages, said assembly including a first tubular body landable in said upper space when said assembly has been so lowered, a second tubular body, means connecting the first and second bodies against vertical movement re1ative to one another, said second tubular body having means thereon releasably attachable to a running tool to permit the assembly to be lowered into the bore of the casing head upon manipulation of said running tool so as to land the first body in said upper space, oppositely facing shoulders on the first and second bodies on one side of the assembly, a seal ring disposed between said shoulders, said connecting means being releasable upon landing of said first body and further manipulation of said running tool to permit said second body to be moved downwardly relative to the first body so as to deform said seal ring into sealing engagement with the Wall opposite to said one side of the assembly, means for sealing between the other side of said assembly and the wall 0pposite thereto, and means on said assembly operable in response to manipulation of the running tool for anchoring said first body in its landed position within said bore and said second body in its lowered position relative to the first body.

16. Wellhead apparatus of the character defined in claim 15, wherein the anchoring means is releasable in response to still further manipulation of said running tool so as to permit said second body to be moved upwardly relative to the first body, whereby said seal ring may retract from deformed position and said first body may be raised from landed position.

17. Wellhead apparatus of the character defined in claim 15, wherein said anchoring means includes parts on the outer side of the assembly movable into locking engagement with the bore of the casing head upon deformation of said seal ring due to downward movement of said second body relative to the first body.

18. Wellhead apparatus of the character defined in claim 16, including means for supporting said first body from the second body for upward movement therewith, as said second body is moved upwardly upon release of said anchoring means, to permit said first body to be raised from within the bore with said second body by means of said running tool.

19. Wellhead apparatus of the character defined in claim 15, wherein said connecting means comprises a shear pin.

20. Wellhead apparatus, comprising a casing head having a bore therethrough with an upper cylindrical portion, said cylindrical bore portion having a seat at its lower end and an annular groove above the seat, a casing hanger landable on the seat for suspending a casing from its lower end, means providing flow passages connecting annular spaces between the hanger and bore above and below the seat, and an assembly lowerable within the bore for clos- 17 ing the upper annular space above the upper end of said passages, said assembly including a first tubular body landable in said upper space when said assembly has been so lowered and a second tubular body arranged concentrically of and supporting said first body, means on said second body releasably attachable to a running tool to permit said assembly to be lowered within the casing head bore, upon manipulation of said running tool, so as to land said first body in said upper space, a seal ring disposed between oppositely facing shoulders on the outer sides of the first and second bodies, a rigid, radially expansible ring carried about the outer side of said assembly between one a of said shoulders and said seal ring, said second body being movable vertically downwardly with respect to the first body, upon landing of said first body and further manipulation of said running tool, so as to deform said seal ring outwardly into sealing engagement with said bore above the upper end of said passages and expand said rigid ring outwardly into load transmitting engagement between said second body and the lower end of said groove, means for sealing between the inner side of said assembly and said hanger, and means on said assembly operable, in response to said manipulation of the running tool, for anchoring said first body in its landed position and said second body in its lowered position relative to the first body.

21. Wellhead apparatus of the character defined in 20, wherein the shoulder on said first body tapers downwardly and outwardly and the rigid ring is supported thereon, the lower end of the groove in said bore tapers downward-1y and inwardly, and the rigid ring has inner and outor tapering surfaces at its lower end corresponding to said first body shoulder and lower end of the groove, respectively.

22. Wellhead apparatus of the character defined in claim 21, wherein said second body is disposed about the upper end of the first body, and there is an expander ring about the first body beneath the seal ring and above the rigid ring, said expander ring having an inwardly and downwardly tapering surface on its lower end engaging with the co responding surface on the upper end of the rigid ring.

23. Wellhead apparatus, comprising a casing head having a bore t-herethrough with an upper cylindrical portion, said cylindrical bore portion having a seat at its lower end and an annular groove above the seat, a casing hanger landable on the seat for suspending a casing from its lower end, means providing flow passages connecting annular spaces between the hanger and bore above and below the seat, and an assembly including body means releasably attachable to a running tool for lowering said assembly within the bore and into landed position closing the upper annular space above the upper ends of said flow passages, means on said body means for anchoring said assembly in said landed position upon further manipulation of said running tool, means on said body means for sealing between its inner side and said hanger, when said assembly is so landed, a seal ring and a rigid, radially expansible ring about the outer side of said body means, and means on said body means operable, upon landing of said assembly and said further manipulation of said running tool, to expand said seal ring into sealing engagement with the outer side of said body means and said bore and said rigid ring into load transmitting engagement between said body means and the lower end of said groove.

24. Wellhead apparatus, comprising a casing head having a bore therethrough with an upper cylindrical portion, said cylindrical bore portion having a seat at its lower end and an annular groove above the seat, a casing hanger having a seat landa'ble on the seat in the head and an upwardly extending tubular extension which defines an annular space between it and the bore, and an assembly for closing the space including a seal ring, a rigid, radially expansible ring beneath the seal ring, an expander ring intermediate the seal ring and the rigid ring, and means for expanding the seal ring outwardly into sealing engagement with said bore and moving said expander ring downwardly to expand said rigid ring outwardly into load transmitting engagement between said expander ring and the lower end of said groove.

References Cited UNITED STATES PATENTS 859,304 7/1907 Larken et al. 166-196 3,139,141 6/1964 Fredd et al 166-125 X 3,268,241 8/1966 Castor et al. 285139 3,268,242 8/1966 Bishop et al 285l42 3,268,243 8/1966 Word 285l42 3,273,646 9/1966 Walker 285140 X ERNEST R. PURSER, Primary Examiner. 

